Vera Caslavska, Czechoslovakia's most decorated Olympic athlete and a vocal critic of communism who was persecuted for her dissent, has died at the age of 74.

The head of the Czech Olympic Committee said on August 31 that Caslavska had passed away a day earlier after battling pancreatic cancer for more than a year.

"Vera was a fighter. She was diagnosed last year in the spring.... When she did not come with us to Rio it was clear the situation was bad," Jiri Kejval told the Reuters news agency, referring to the Summer Olympics in August in Brazil.

Born on May 3, 1942 in Prague, Caslavska claimed her first Olympic medal -- a silver -- at the 1960 Rome Games.

It was four years later, however, when her gold rush began.

Caslavska wowed the world with her performances at the Olympics in Tokyo in 1964 and Mexico City in 1968, winning 10 medals including seven golds.

Her total medal haul of 11 made Caslavska Czechoslovakia's most decorated Olympic athlete ever. No Czech or Slovak athlete has won as many Olympic medals since the country split in two in 1993.

Sports success was always welcomed by the communist regimes of Eastern Europe and the Soviet Union, which saw it as proof of what they told citizens was their superiority over the capitalist West.

But Caslavska was not toasted back at home for her Olympic achievements.

She was an opponent of Czechoslovakia's regime and an outspoken backer of Alexander Dubcek's liberal reforms aimed at democratizing the communist system in the short-lived era known as the Prague Spring.

Vera Caslavska in later life

Caslavska signed the Two Thousand Words Manifesto, a key document of the Prague Spring that was published in June 1968.

Hundreds of thousands of people signed the document, demanding freedom of speech and the removal of hard-line Communist Party apparatchiks.

The manifesto angered Soviet leader Leonid Brezhnev, who ordered Warsaw Pact troops to invade Czechoslovakia to crush the reforms in August 1968.

To protest the invasion, Caslavska held a silent protest at the 1968 Olympic Games, held in October in Mexico City. During a medal ceremony, Caslavska looked down and away when the national anthem of the Soviet Union was played. Her subtle gesture won her respect from many compatriots, but scorn from Czechoslovakia's leaders.

WATCH: Vera Caslavska's Silent Protest At The 1968 Olympics

Following the 1968 Games, Caslavska faced persecution at home and was denied the right to work or travel. It wasn't until 1974 that she was allowed to work as a coach in Czechoslovakia.

After the fall of communism in 1989, Caslavska began to gain the official recognition she had been denied for so long. Vaclav Havel, the first post-communist Czechoslovak and then Czech president, named her as an adviser. Caslavska was elected president of the Czechoslovak and later of the Czech Olympic Committee.

She received the UN's Pierre de Coubertin Prize for promoting fair play in 1989 and was also awarded the Olympic Order.

Caslavska's death from pancreatic cancer came after a tough and lengthy battle, including an eight-hour operation in May 2015 and chemotherapy.

One of the first to announce Caslavska's death was the Czech journalist and author Pavel Kosatik in a Facebook post.

Sommerova told Czech Radio that the country had lost one of the "greatest Czechs we ever had."

Caslavska faced tribulations in her personal life as well.

Her marriage with Josef Odlozil, an athlete whom she married during the Mexico Games, ended in the 1980s. Her son, Martin, was found guilty of assault that led to his father's death in 1993. He was sentenced to four years in prison, but shortly thereafter pardoned by Havel.

At the time, Caslavska was treated for depression and withdrew from public life.